The purpose of the proposed research is to determine how the comparative benefits and risks to the mother and to the child are affected by the choice of delivery technique when the infant is in the breech position. Specifically we propose to determine how the relative benefits of cesarean and vaginal delivery are affected by the gestational age of the fetus. The data to be used have been collected from 75 hospitals. Over 7,000 breech births are avilable for analysis; all multiple gestations, life-treatening congenital anomalies and antepartum deaths have already been removed. Each breech presentation is paired with a vertex presentation vaginally delivered from the sam ehospital, born about the same date with the mother in same age/parity category. Again, multiple gestations, congenital anomalies, antepartum deaths have been removed from the available pool of vertex presentations. Analysis of a rare event requires a large data set if the analysis is to be more than superficial. Researc using a large number of breech presentations has previously involved aggregation over time, so that simultaneous improvements in intrapartum fetal care and neonatal intensive care have confused the issue. This research proposes instead to aggregate data over a variety of geographical locations, which has some of the same limitations. The 75 hospitals have different resources available to care for the high risk mother and/or infant, as well as different propensities to deliver abdominally. The technique of matched pairs is intended to overcome this difficulty. The vertex presentations represent a minimum risk group whose mortality and morbidity rates (maternal and infant) can be expected to represent the ideal for those hospitals. The four groups ( cesarean breech, vaginal breck, vaginal vertex paired withi cesarean breech, and the vaginal vertex paired with vaginal breech will be compared with respect to the survival of the infants, the 5-minute Apgar score, neonatal morbidity, maternal mortality and morbidity. Variables used as controls will include type of breech, birthweight, gestation, parity and social characteristics of the mother. The statistical methodology applied is weighted least squares (GSK) analysis of categorical data.